High-pressure fuel pumps are known for pressurizing fuel sucked in a pressure chamber by reciprocal motion of a plunger, in which, when a fuel delivery pressure is more than a predetermined pressure, a relief valve opens to reduce the fuel delivery pressure. This type of fuel pump is disclosed, for example, in JP-2003-247474A, JP-11-200990A and JP-2004-138062A. However, manufacture of this conventional high-pressure pump provided with such a relief valve can be overly time-consuming.
For example, since an exclusive hole for accommodating the relief valve is formed in a pump housing in JP-2003-247474A, JP-11-200990A and JP-2004-138062A, manufacturing time for forming the accommodating hole of the relief valve increases. In addition, since the relief valve is accommodated in the exclusive hole, it may be required to seal the accommodating hole of the relief valve or a clearance between the accommodating hole and the relief valve with a sealing member or the like in addition to sealing locations other than the accommodation location of the relief valve. This results in an increase in the number of sealing locations of the relief valve, thereby increasing manufacturing time for sealing.
In addition, in fuel pumps with a relief valve in an exclusive hole of a housing (see, e.g., FIG. 2 of JP-11-200990A), the housing is divided into a plurality of housing members for accommodating the relief valve. When the pump housing includes a plurality of the housing members for accommodating the relief valve, a clamping member or the like is used to assemble the housing members with each other, thereby increasing the assembly time of the pump housing.
In addition, for discharging the delivery fuel from the relief valve, a fuel discharge passage is included for communicating a delivery port with a delivery port side of the relief valve. However, it is difficult to form such a fuel discharge passage inside the pump housing. Therefore, manufacturing becomes more difficult and more time consuming.
In addition, when the fuel discharge passage is formed exclusively for discharging the delivery fuel from the relief valve, the manufacture time for forming the fuel discharge passage in the pump housing increases.
In this way, the manufacturing time and the sealing time of the accommodating hole in the relief valve, the assembly time of the pump housing, and the manufacturing time of the fuel discharge passage is significant, and as a result, manufacturing time of the high-pressure fuel pump is significant.
Further, decreasing the size of the conventional high-pressure fuel pump can be difficult.
For instance, in a case of accommodating a relief valve in an exclusive hole, a space for forming the exclusive hole is included in the pump housing, thereby increasing the size of the pump housing. In addition, in a case of sealing a clearance between the exclusive hole of the relief valve and the relief valve with a sealing member such as an O-ring, a location space for the sealing member is included, therefore increasing the size of the pump housing.
Further, in a structure of clamping a plurality of housing members for accommodating the relief valve, a seal dimension in the assembling location of the housing members each other is substantially long, thereby increasing the size of the pump housing.
In view of the above, there remains a need for a high-pressure fuel pump that overcomes the above mentioned problems in the conventional art. The present disclosure addresses this need in the conventional art as well as other needs, which will become apparent to those skilled in the art.